I did the opposite -- switched from SmugMug to Zenfolio some years ago and haven't looked back since. It was a hassle transferring the images from one site to the other, but it was doable. What I did was to use both services for a while until I was really sure which one I preferred, and then made the switch. If I recall correctly, it was at the time that Smugmug was raising its fees and also I found that it was much quicker and easier to grab an image and share it on another site (usually a web-based forum such as this one) with Zenfolio than it was with Smugmug. Still is. With regard to fees, I pay $40.00/yr for Zenfolio, which I think is the basic level, since I don't really need to store my RAW images or set up arrangements for selling my photos through them. I don't do videos at all. I was an early subscriber to Zenfolio, back when it was first starting up, and I think my fee is also based on that as well.
As for Flickr, I had an account that I just used for odds-and-ends of images a long time ago back in the day when it was a totally free service. None of the images was all that important to me and since I don't recall now the account name or the email address I used for it, I guess that account will be going by the wayside, if it hadn't already at the time they began charging fees, which is fine with me. I didn't realize that Flickr gives 1 TB free now....must've happened after their initial change to being fee-based?